Moleschott studied medicine (1842–45) at the University of Heidelberg in Germany. He worked for a time in Utrecht as a general practitioner and continued his studies. From 1847 to 1854 he was a Privatdozent at the University of Heidelberg; he resigned when he came up against the “official philosophy” of German universities, which held that speculation about consciousness and similar topics was not the proper pursuit of the university. Moleschott had also scandalized the university authorities by speaking out in favour of cremation. In 1856 he was appointed professor of physiology at the University of Zürich. While there he founded a journal, Untersuchungen zur Naturlehre des Menschen und der Thiere (1857–94; “Research on the Natural Philosophy of Man and the Animals”). In 1861 he was appointed professor of experimental physiology and physiological chemistry at Turin, and in 1879 he accepted a professorship in Rome. He became an Italian citizen.

Moleschott’s researches, especially those on blood and metabolism, were instrumental in the development of the field of physiological chemistry. He espoused the theory that even emotions and thoughts had a physiological basis and was noted for the statement “no phosphorus, no thought.”